Two professors from Wharton and Stanford suggest that mergers — and the accompanying mania — may result from overconfidence. Instead of contending that mergers and acquisitions stem from senior leaders’ empire-building inclinations — a stance many skeptics take — Geoffrey Tate and Ulrike Malmendier offer that instead of putting their own interests ahead of shareholders’ — those leaders just might not have an accurate sense of their own abilities, as well as their companies’ prospects.